1. Field of the Invention
The present invention relates to a process for the preparation of high molecular weight organopolysiloxanes by polymerization and rearrangement of low molecular weight organopolysiloxane compounds, especially those which are cyclic.
2. Description of the Prior Art
It is known to the art that it is possible to polymerize and to rearrange low molecular weight organopolysiloxanes in order to convert them into high molecular weight products by using basic catalysts, such as, for example, alkali metal hydroxides, alkali metal silanolates and alcoholates, or quaternary ammonium hydroxides (NOLL -- Chemistry and Technology of Silicones -- 1968 Ed. p. 206). Various techniques have been proposed with a view towards speeding up the polymerization rate, for example, via the use of nitrites or amides (French Pat. Nos. 1,354,443 an 1,359,414). It has also been proposed to associate an aminophosphine oxide (French Pat. No. 1,474,899), or a complex of an alkali metal with a triaminophosphine oxide (French Pat. No. 1,474,900), with the basic catalyst.
Additionally, Boileau et al. have shown (POLYMER LETTERS, 12, p. 217-220 -- 1974) that it was possible to rapidly polymerize hexamethylcyclotrisiloxane, in the presence of potassium hydroxide complexed with a macroheterobicyclic ether (complexes termed cryptates). Boileau et al. have carried out the reaction in benzene, using a large quantity of alkaline catalyst and of "cryptate", relative to the quantity of cyclic siloxane employed.